ABSTRAK
Informasi curah hujan diperlukan untuk memperkirakan ketinggian air yang
masuk ke Daerah Aliran Sungai (DAS). Informasi tersebut dapat diperoleh de-
ngan meramalkan curah hujan. Tujuan penelitian ini adalah menentukan model
yang digunakan dalam peramalan curah hujan dan klasi_kasi peramalan curah
hujan tahun 2015 di DAS Bengawan Solo.
Peramalan curah hujan yang mempunyai pola data musiman dapat meng-
gunakan model runtun waktu fuzzy dengan pembobot eksponensial. Residu dari
model runtun waktu fuzzy terbobot diestimasi menggunakan deret Fourier untuk
memperoleh residu yang lebih kecil. Model hibrida runtun waktu fuzzy terbobot-
deret Fourier digunakan untuk meramalkan curah hujan tahun 2015. Klasi_kasi
peramalan curah hujan di DAS Bengawan Solo ditentukan berdasarkan ukuran
Badan Meteorologi Klimatologi dan Geo_sika (BMKG).
Berdasarkan hasil penelitian, peramalan curah hujan di DAS Bengawan So-
lo dengan model hibrida runtun waktu fuzzy terbobot-deret Fourier menunjukkan
Root Mean Square Error (RMSE) yang terkecil. Hasil klasi_kasi peramalan cu-
rah hujan tahun 2015 bulan Mei, Juni, Juli, Agustus, September, Oktober dika-
tegorikan rendah, bulan November dikategorikan menengah dan bulan Desember
dikategorikan tinggi.
Kata Kunci : model runtun waktu fuzzy terbobot, deret Fourier, curah hujan,
DAS Bengawan Solo
ABSTRACT
Rainfall information is needed to forecast the water height that ows into
river watershed. It's can be obtained by forecasting rainfall. The purpose of this
study was to determine the best model among several models in forecasting and
classifying 2015's rainfall in Bengawan Solo watershed.
The forecasting of rainfall having seasonal data pattern can be using the
fuzzy time series model with an exponential weight. Residual of weighted fuzzy
time series model was estimated by Fourier series to obtain a smaller residual
value. A hybrid model of weighted fuzzy time series-Fourier was used to forecast
2015's rainfall. Classifying rainfall in Bengawan Solo watershed based on Badan
Meteorologi Klimatologi dan Geo_sika (BMKG)'s criterion.
Based on the result of this research, rainfall forecasting with the hybrid
model of weighted fuzzy time series-Fourier showed the smallest Root Mean Squ-
are Error (RMSE). Forecast classi_cation showed 2015's rainfall in May, June,
July, August, September and October was categorized as low, in November was
categorized as average, and in Desember was categorized as high.
Keywords : weighted fuzzy time series model, Fourier series, rainfall, Bengawan
Solo watershed